1. Field of the Invention
The present invention relates to automatically operated steps for large machinery such as road graders and earthworking equipment.
2. Prior Art
In the prior art road graders, for example, have had fixed steps or else have had steps which will merely fold out of the way during use. As the equipment becomes larger and larger, the effort required to use the steps is substantial. In many cases the steps have to be recessed back inwardly from the periphery of the vehicle to keep them from being damaged, so that they are extremely difficult to use.
Folding steps for travel trailers etc. have been advanced, but these merely move the steps out of the way when not in use.
Platforms have been used for raising loads up to truck beds, comprising hydraulically operated tailgates that use a parallel linkage for operation. Such linkage for a load tailgate is shown in U.S. Pat. No. 3,233,758, and various other similar devices show parallel linkages for raising a platform. Typical of these include U.S. Pat. Nos. 2,576,881; 3,589,537; 3,077,275; 2,701,656; and 2,656,058. A folding ladder is shown in U.S. Pat No. 3,869,022, and a retractable step using an electric motor for retraction is shown in U.S. Pat. No. 3,887,217. However, none of these show an elevating type of step that can be used by an operator to simply and easily raise himself to a level position with an operator's cab of large earthworking equipment.